Java implementation of random verification code function example code

The random code function added in the registration, login or release information modules of many systems is to avoid the use of automatic registration programs or automatic release programs. In fact, the verification code is to randomly select some characters and display them on the page in the form of pictures. If the characters on the picture need to be submitted at the same time when downloading and submitting the tomato garden XP system, if the submitted characters are different from those saved in the server session, the submitted information is considered invalid. In order to avoid automatic program analysis of pictures, some interference lines are usually randomly generated on the pictures or characters are distorted, which increases the difficulty of automatic recognition.